In this paper, calibration modeling of a low-cost Inertial Measurement Unit (IMU) sensor for Small Unmanned Aerial Vehicle (SUAV) attitude estimation is considered. First, an Allan variance analysis method is used to determine stochastic noise model parameters for each sensor of a Micro-Electro-Mechanical-System (MEMS) IMU. Next, these models are included in a Global Positioning System/Inertial Navigation System (GPS/INS) sensor fusion algorithm for on-line calibration. In addition, an off-line magnetometer calibration is considered that uses a set of GPS/INS sensor fusion attitude estimates to derive a calibration model. This off-line magnetometer calibration model is then augmented on-line with sensor fusion estimates of the residual sensor biases. Finally, using the calibrated magnetometers, attitude estimation is considered that uses only a low-cost IMU with magnetometers. Each sensor fusion algorithm is formulated using an Unscented Kalman Filter (UKF). For performance validation, attitude estimates are calculated with data collected on-board a SUAV and are compared with high-quality vertical gyroscope measurements.
NomenclatureA = Allan variance a x,y,z = specific-force in the aircraft body-axis (m/s 2 ) B = body-axis b = sensor bias f = state transition function h = observation function F s = sampling frequency g = acceleration due to gravity (m/s 2 ) j = counting index k = discrete-time index M = magnetometer measurement n = white driving noise p = roll rate (deg/s) q = pitch rate (deg/s) r = yaw rate (deg/s) x = position in the local South direction (m) x = state vector y = position in the local East direction (m) z = position in the local up direction (m) z = measurement vector Q = process-noise covariance matrix R = measurement-noise covariance matrix 2 T = averaging time (s) Ts = sampling time (s) u = input vector V x,y,z = velocity in the local south, east, up directions (m/s) w = wide-band noise Ω = averaged bin Θ = parameter vector θ = aircraft pitch angle (deg) σ = standard deviation τ = correlation time (s) ϕ = aircraft roll angle (deg) ψ = aircraft heading angle (deg)